A new study investigates how anger associated with delusions — not simply being out of touch with reality — is critical in determining whether psychosis turns violent.

The research, published in JAMA Psychiatry, included 458 participants around age 31 who experienced a first episode of psychosis in East London, an inner-city neighborhood with a history of poverty and social stress, between 1996 and 2000. They were diagnosed with some sort of psychosis either through local mental-health services and hospitals or via the criminal-justice system.

Schizophrenia and schizoaffective disorder — a condition that includes the delusions and social withdrawal of schizophrenia, along with a mood conditions like depression or bipolar disorder— together accounted for more than half of the participants’ diagnoses. However, 14% suffered from psychotic depression, a condition in which delusions develop as part of a severe depression, and 10% had bipolar disorder in which a manic episode included psychotic delusions. The rest were diagnosed with a variety of less common psychotic conditions.

Nearly two-thirds of the participants were not involved in any violence at all in the year before their first psychotic episode. But 26% had committed what the authors defined as minor violent acts, including assaults that did not lead to injuries or involve weapons. Another 12% were seriously violent, engaging in crimes like injurious assaults, use of lethal weapons or sexual attacks.

The researchers, led by Dr. Jeremy Coid, a professor of psychiatry at Queen Mary University in London, interviewed participants about the content of their delusions and their emotional experiences. Anger related to delusions was strongly linked with attempting to harm others. After adjusting for other factors, 31% of the minor violence could be attributed to anger connected with delusions. In the seriously violent patients, anger accounted for 56% of the incidents. Elation, anxiety and fear were not associated with violence.

Those who engaged in violence also tended to be younger and were more than twice as likely to have taken drugs in the past year, although alcohol use did not matter. The seriously violent were far more likely to be male, but there was no difference in risk by gender for minor violence.

None of the delusions were dangerous in and of themselves. But three types, all of which involved a sense of personal threat, were linked to serious violence if they provoked anger. One delusion centered on the idea that the person was being spied on or was under surveillance by some type of threatening authority, group or person. Another focused on the misguided belief that people with hostile intent were targeting the victim. Finally, there was the fantasy of some sort of conspiracy against the delusional person.

Any anger generated from feeling threatened under these situations could make the patients lash out. “Anger due to delusions appeared to constitute the main drive to serious violence,” the study authors write. On the other hand, a more depressive response to the threats seemed to thwart violence so that a “depressive affect had a protective effect,” according to the research.

“If patients are not angry, the delusions themselves don’t cause a problem,” Coid told the New York Times. What causes delusions to result in angry responses in some people and not in others? Researchers aren’t sure, but they believe that a better understanding of this connection, as well as a greater appreciation for how this anger response is related to the delusions of psychosis, could lead to treatments that prevent violent behavior and its potentially tragic consequences.